Force sync is not resetting beacons. It is only telling beacon to exchange information with the Cloud. If you want to reset them keep side button pressed and then press main button 8 times.
In the first post you wrote that you see them in Estimote App. It crashes, but it is still able to scan them. Now you claim that they are also not discoverable on iPhone. So they were advertising and now they stopped? You may try to use different scanning app like nRF Connect to confirm that.
Have you tried to connect to those beacons via WebIDE using different computer (preferably Mac)?